Strip seals, which are also known as feather seals, can be used to eliminate leakage flow between two components arranged adjacently to one another. This is achieved by the two components having groove recesses in edge faces that lie substantially opposite and adjacent to one another. The strip seal seals the gap between the two components by being at least partially received into the groove recesses of the adjacently fitted components so as to span the gap between the components. U.S. Pat. No. 5,531,457 discloses an example of such a strip seal used to reduce leakage flow through the gap between two platforms of a blade.
The grooved recesses of fitted components often do not perfectly align due to, for example, manufacturing tolerances or as a result of thermal expansion. If the strip seal is manufactured so as to tightly fit into the groove recesses, a less than perfect groove recess alignment would result in high stress loading of the strip seal, which can result in premature failure.
In recognition of this drawback, strip seals can be made thinner than the height of the grooved recesses and flexible orthogonal to the strip seal length. In operation, the pressure differential across the seal, due to the flexibility of the strip seal, forces the strip seal against one surface of the grooved recess to effect a seal. When the pressure differential is low, strip seals are made thinner so as to increase their flexibility strip. To hold thin seals in place, for example during installation, the strip seal may be provided with biasing means which can be dispersed along the strip seal length. An example of biasing means is described in U.S. Pat. No. 3,836,279.
During operation, the strip seals can be exposed to periodic pressure pulsations caused by the passing of rotating blades as they pass the non-rotating regions within which the strip seals are contained. Depending on the strength and frequencies of the pressure pulsations, parts of the strip seal that are not biased against faces of the groove recess or otherwise retained can be induced into periodic resonance leading to premature fatigue failure of the strip seal. An application where this drawback is particularly relevant is in the sealing of components in gas turbines where rotating blades of the gas turbine induce pressure pulsation at sealing faces.
By reducing the seal length, it is possible to avoid fatigue failure. However, when strip seal length is shorter than the length of the recess groove, sealing is made more complicated. There is therefore a desire for a strip seal which is resilient to fatigue failure induced by pressure pulsation independent of strip seal length.